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High-fat diets have been associated with overweight/obesity and increased mortality in middle-aged populations. However, it is still unclear how gut microbiota in middle-aged populations responds to dietary fats at a normal dose. In this study, we explored gut microbiota structure in middle-aged rats (aged 12 months) after feeding 4% (w/w) soybean oil, lard or fish oil for 3 months, respectively. The results showed that the gut microbiota structure in the fish oil group was substantially different from those of the soybean oil and lard groups in both in vitro and in vivo studies. The relative abundances of phylum Proteobacteria and genus Desulfovibrio in the caecal and colonic contents were the highest in the fish oil group (p

A sulphate-reducing culture of the genus Desulfovibrio was directly inhibited by the hydrogen sulphide (H2S) produced. Batch experiments carried out at pH 6.2 and 6.6 show that complete inhibition is achieved for almost the same H2S concentration of approximately 550 mg/l.

The three types of hydrogenase hitherto characterized in genus Desulfovibrio exhibit distinctive inhibition patterns of their proton-deuterium exchange activity by CO, NO and NO2-. The (Fe) and (NiFeSe) hydrogenases are the most sensitive to all three inhibitors while the (NiFe) enzymes, relatively little inhibited by CO, are still very sensitive to NO but unaffected by NO2-. These differences together with some specific catalytic properties, in particular the pH profile and the H2 to HD ratio in the exchange reaction, constitute a simple means of characterizing multiple hydrogenases present in one or different species.

SUMMARY: Fourteen previously unstudied strains of the genus Desulfovibrio and eight thermophilic strains of the genus Desulfotomaculum were allotted to species on the results of physiological and biochemical tests. On DNA base composition the Desulfovibrio strains fell clearly into three groups, corresponding to Dv. salexigens, Dv. desulfuricans and Dv. vulgaris. NaCl-dependence appeared to be a constant and unique feature of Dv. salexigens strains, and ‘sulphate-free’ growth on pyruvate a constant characteristic of Dv. desulfuricans, although one strain of Dv. vulgaris also dismuted pyruvate. Fumarate dismutation showed no species correlation. ‘Sulphate-free’ growth on choline was often minimal and the test appeared to be of little value. A high degree of resistance to Hibitane was not a constant characteristic of Dv. salexigens. The thermophilic strains showed great uniformity in DNA base composition, Hibitane resistance and ‘sulphate-free’ growth, and were all classified as Desulfotomaculum nigrificans.

Determinative studies were carried out on an obligatory anaerobic, sulfate- reducing bacterium (strain No. 61) isolated from a pond water in Skarvs Nes district in the East Antarctica. This sulfate-reducing bacterium was nonsporulating, sigmoid or straight rods with a single polar flagellum, gram negative, and possessed cytochrome c3 and desulfoviridin, characteristic of the genus Desulfovibrio. It could grow with lactate, malate, pyruvate, or choline when sulfate was present in the culture medium and had a stable sodium chloride requirement. These observations dinicated that strain No. 61 closely resembled Desulfovibrio desulfuricans var. aestuarii.

A reevaluation of the original buoyant density conversion formula used to calculate the molar percentage guanosine + cytosine (% G + C) contents of the accepted species of genus Desulfovibrio has been undertaken. It would appear that the formula used gives values 4–5% lower than those obtained using formulae more generally cited in modern literature. Recalculations of % G + C content values for Desulfovibrio DNA are presented using the formulae of three different workers, and are compared with those values originally used in the classification of genus Desulfovibrio.

A comparison of amino-terminal amino acid sequences from the large and small subunits of hydrogenases from Desulfovibrio reveals significant differences. These results, in conjunction with antibody analyses, clearly indicate that the iron, iron + nickel, and iron + nickel + selenium containing hydrogenases represent three distinct classes of hydrogenase in Desulfovibrio.